Irresistibly and dangerously attracted to something or someone.
Origin
The phrase is a simple allusion to the well-known attraction that moths have to bright lights. The word moth was used the the 17th century to mean someone who was apt to be tempted by something that would lead to their downfall.
'I destroy the image after I've made it,' said Turbeville. 'Obliterate it a little so you never have it completely there.' It's a quite un-American world, a view through the rear window, fascinated by the beaten, worn and forgotten.